The effects of the volume fraction on the jamming or unjamming transition have attracted considerable interest in many studies. When increasing the volume fraction, or decreasing the shear stress and temperature, systems tend to go from unjammed to jammed states. Three parameters influence the jammed states: volume fraction, shear stress, and temperature. However, the elastic modulus becomes nonzero for a solid-like jammed system because the phase lag is between 0° and 90°, which means that a system deformed by external forces has a tendency to recover its original shape when the forces are removed. For liquid, the elastic modulus is zero because the phase lag is 90°. The elastic modulus, determined by the phase lag between strain and stress under oscillatory shear flow, is one factor that can analyze the transition. 1–3 Especially, the rheological properties of blood as a colloidal suspension have great effects on the blood pressure and wall shear stress related to the cardiovascular diseases. Understanding the mechanism of this transition is of great interest in many research areas in the food, polymer, biomedical, and lubrication industries. –The emulsions of these systems will tighten as they are exposed to downhole temperatures and sheared through the bit.A broad range of rheological materials, such as foams, granular materials, emulsions, and colloidal suspensions, can undergo a transition between a flowing liquid-like (unjammed) state and a nonequilibrium disordered solid (jammed) state. Freshly mixed, invert-emulsion muds usually have low electrical stabilities when shipped from the liquid mud plant, even though they are adequately treated with emulsifiers.Factors that can influence the electrical stability are:.The unit of measure for recording the electrical stability is volts.The stronger the emulsion, the higher the voltage required to break down the emulsion completing the electrical circuit to conduct electricity.In the electrical stability test, the voltage (electrical potential) is increased across electrodes on a fixed-width probe until the emulsified water droplets connect (i.e., coalesce) to form a continuous bridge or circuit. –Oil and the synthetic fluids do not conduct electricity. –Higher values indicate a stronger emulsion and more stable fluid. The electrical stability is an indication of how well (or tightly) the water is emulsified in the oil or synthetic phase.–Changing the ratio is not used to alter either of these properties. The viscosity and HTHP filtrate will change with changes in the oil-or synthetic-to-water ratio.When using oil or synthetic muds, all water hoses on the pits should be disconnected or plugged to prevent accidental contamination with water.–A rapid decrease in the O/W or S/W ratio indicates an influx of saltwater from the formation, and a pit volume increase should have been observed. The O/W ratio remains constant when the mud is weighted up or solids are incorporated into the mud, even though the volume percent liquid is decreased significantly. ![]() –Oil ratio (O) = (vol% oil)/(vol% oil + vol% water) x 100 The calculation of the oil-to-water ratio requires retort values as follows:.–Different conditions favor the use of different ratios, so there is no ratio that must be used for any set of conditions. –Generally, higher mud weights require higher ratios. –The oil-or synthetic to-water ratio relates the oil and water fractions to the total liquid fraction. The oil-or synthetic-to-water (O/W or S/W) ratio relates only to the liquid portion of the mud and is not affected by the solids content.
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